Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$220.39	10.869%	$244.3442	$244.34	$244.35	$244.30
Purchase #2	$244.36	6.779%	$260.9252	$260.93	$260.95	$260.90
Purchase #3	$230.59	9.864%	$253.3354	$253.34	$253.35	$253.30
Purchase #4	$150.61	9.774%	$165.3306	$165.33	$165.35	$165.30
Purchase #5	$170.33	12.375%	$191.4083	$191.41	$191.40	$191.40
Purchase #6	$201.87	12.835%	$227.78	$227.78	$227.80	$227.80
Purchase #7	$247.43	13.541%	$280.9345	$280.93	$280.95	$280.90
7 purchase totals =	$1,465.58		$1,624.0582	$1,624.06	$1,624.15	$1,623.90